User's Manual

is always associated with one and only one downstream. The association of one or
more upstream logical channel with a downstream logical channel is made in the
CMTS configuration. Upstream logical channels from one or more Access Point
Transceivers may not
be combined into a single upstream input to the CMTS.
3.4.2 Upstream Frequencies
The cable modem at the customer site obeys the various protocols within the cable
plant. One of these determines the frequency that the cable modem operates on for
both upstream and downstream.
The CPE Transceiver modulates the modem upstream output and puts it over the air
in the 5.3 GHz ISM band as a double-sideband signal. The Access Point Receiver
is tuned to one of the carriers. The AP Receiver demodulates the received
frequency down into the same cable frequency the modem transmitted, and places it
on the cable system.
3.4.3 Available Frequencies
All wireless modems in the same Access Point sector must transmit upstream on the
same frequency, and each wireless modem can operate on only one upstream
channel.
The Upstream data rate is 5.12 Mbps with Channel Bandwidth of 3.2 MHz.
Table 3-2 shows the modem Upstream frequencies, and the corresponding
Upstream Air frequency used by the subscriber transducer.
The CMTS commands the wireless modem to its Upstream Transmit Carrier
frequency during the wireless modem registration process. These are configuration
parameters that are set in the CMTS network management system. See the
software installation guide for that product.
Some operators combine multiple Upstreams from different nodes. This may dictate
the upstream channel for the wireless modems. Combining Upstreams tends to
save on capital equipment, but will limit the traffic that can be carried. This balance
of cost/performance tradeoff is usually different for business customers than
residential customers.
ARCXtend manual, August 2003 3-8